1. Field of the Invention
The present invention relates to an image reading apparatus.
2. Description of the Related Art
There is known a conventional image reading apparatus which causes a reading unit to execute a reading operation to read an original while changing a relative position between the reading unit and the original. For example, there is known an image recording apparatus which reads an original by causing a reading unit to execute the reading operation at a predetermined time interval while conveying the reading unit or the original at a constant velocity.
There is known another image reading apparatus which reads an original by causing the reading unit to perform the reading operation each time a motor changing the relative position between the reading unit and the original is rotated by a predetermined amount (see, for example, Japanese Patent Application Laid-open No. 2011-44783).
In this image reading apparatus, a shift pulse is inputted to the reading unit each time the motor is rotated by the predetermined amount. Each time the shift pulse is inputted to the reading unit, the reading unit transmits electric charge accumulated in a photoelectric conversion element to a shift resistor.
The electric charge to be transmitted is generated by the photoelectric effect during a time period from the previous shift pulse to the current shift pulse. The information of the electric charge is converted to an image data corresponding to one line of the original. The transmission causes initialization of the accumulated electric charge in the photoelectric conversion element, and in the reading unit, a new reading operation for accumulating the electric charge is started.